Choice "C" is correct. Release of a co-surety is treated the same as release of security. The release discharges the other co-sureties to the extent of the impairment of their rights. Had West not been released, Quill would have had a right of contribution against West for half of the debt. Thus, Quill is discharged to that extent.
Choice "a" is incorrect. Release of a co-surety is treated the same as release of security. The release discharges the other co-sureties to the extent of the impairment of their rights. Had West not been released, Quill would have had a right of contribution against West for half of the debt. Thus, Quill is discharged to that extent.
Choice "b" is incorrect. Release of a co-surety is treated the same as release of security. The release discharges the other co-sureties to the extent of the impairment of their rights. Had West not been released, Quill would have had a right of contribution against West for half of the debt. Thus, Quill is discharged to that extent.
Choice "d" is incorrect. A principal is not discharged from a debt merely because a surety is released.